How to integral a composite function in yalmip?

sdpvar x1 x2 x3 u1 
% syms x1 x2 x3 u1
d=x1+x2;
y=x1+x2+u1+d;
z=y+3;
t=int(z,y,0,y)

hello everyone...I have define a integration by yalmip, but there are some error..

If replace by syms, there are still errors.

Could you please help me find the mistakes? THANKS.

Answer 1

[infinity]

Hello,

You define z as a function of x1, x2, and u1. But, you apply the integral function to compute the integral of z over the interval [0, y] and told the integral function that the variable of z is also y. It is not correct.

Let image that what you are doing like trying to compute

[Tong Liu]

Thank you for your answer. As you know, z is also a function of y. Why can't I intergral according to y directly? Is that only the final variable like x and u can be used for integration?

Thanks!

[infinity]

Hello,

In case, we have function z(y) = y + 3 then we can compute the integral of z with respect to y as simple by

syms y a
z = y + 3;
res = int(z,y,0,a)

where "a" is upper limit of the integral.

But, in your given code, you defined z as function of x1, x2, u1 and parameter d. Matlab can not understand that z is a function y.

[Tong Liu]

Get it. Thank you for your kindly help!